Alan, Forespar used to make a strobe for about $25 that used one "C" cell. if the one you found is like that, they're quite durable and putting in a dollar battery every year is cheap enough.

The Firefly is no doubt stronger but perhaps needlessly so. And the battery costs, at least on the traditional ones, exhorbitant. I wouldn't ask how long a 20 year old battery can power the light because it is about 15 years overdue to becoming a leaky mess. Replace or toss.